Q: Your column on the five-year-old Ford about replacing the brake control module for $4,000 reminded me of a concern I've had that our technology, especially electronic, is evolving much faster than in the past. During manufacture when this module was being used in current car production, I would guess it cost less than $100 to buy. The price will continue to rise until it becomes uneconomical to build or impossible to repair because the parts that go into it aren't available. When this happens the car is junk! I remember a fuel-injection control module used in several of my '60s Volvos that was troublesome. The replacement cost from the dealer was quite high and salvage yards were picked clean. We may need to encourage car design to take into account longer term repairability.

A: The key word there is "longer term." Have you noticed that the life expectancy of today's automobiles is dramatically longer than just a few decades ago? Instead of being worn out by 100,000 miles, today's motor vehicles, even entry-level cars, can run reliably for 150,000-plus miles without major problems. That doesn't mean engines and transmissions won't fail, but the overall design, manufacturing and quality of modern vehicles are significantly better.

In my opinion there is one major reason for this — computers. From CAD/CAM systems — computer aided design/computer aided manufacturing — to electronic control modules for engines, transmissions, ABS/traction control, HVAC and so many other systems to adaptive engine/transmission management and extensive onboard self-diagnostics, today's cars and trucks are simply much better, more reliable machines with much longer life expectancies.

Until we, as owners and drivers, neglect, abuse and crash them. The majority of vehicles end up in salvage yards because of crashes or corrosion, not mechanical or electronic failure.

By law, carmakers are only required to offer replacement parts for a vehicle for the duration of its original warranty. Fortunately, most components are and will be available used, rebuilt, remanufactured or aftermarket for many additional years. And because so many automotive parts are manufactured by outside suppliers, their continued availability is likely a supply/demand equation.

Electronic components tend to have long life expectancies and require little maintenance, so I think the higher percentage and importance of electronic components in motor vehicles is, on balance, a very good thing.

Q: I have a 2002 Honda CRV. Approximately 6,000 miles ago I had new pads and new rotors installed on all four wheels. Recently I have noticed a clacking sound coming from the left rear brake when the brakes are lightly applied. This happens intermittently, which makes it hard to diagnose. When I take it to the repair shop that did the brake job, they seem baffled. Could it be the rear caliper is getting stuck?

A: In most cases a clicking/clacking noise from a disc brake is caused by movement of the brake pad in its caliper mount. This is most commonly heard when first applying the brakes after a change in direction — forward to reverse or vice versa. Have the shop check the pad's lower retaining clip. If the clip allows the pad to move, replace it.

Q: The manual for my 2013 Nissan Altima with the 3.5-liter engine recommends "unleaded regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91)." I frequent a gas station that offers 87, 89 and 91 octane gas. It shows a formula "R+M/2" for the octane, but it does not say which octane rating it is. Is the octane listed at the pump the AKI or the Research number?

A: In the U.S. and Canada the octane rating shown on the pump is the AKI — anti-knock index. As the formula indicates, the AKI is the average of the research octane number (RON) and the MON (motor octane number), which is more representative of the fuel's behavior under load and is typically 8 to 10 points lower then the RON rating. That explains the 87 AKI/91 RON requirements for your vehicle.